This invention relates in general to rigid axle beams for use in a vehicle suspension system. More specifically, this invention relates to a method of manufacturing a rigid axle beam for use in such a vehicle suspension system.
Virtually all land vehicles in common use, such as automobiles, vans, and trucks, include a frame assembly that is supported upon a plurality of ground-engaging wheels by a resilient suspension system. The structures of known vehicle frame assemblies can be divided into two general categories, namely, separate and unitized. In a typical separate vehicle frame assembly, the structural components of the body portion and the frame portion are separate and independent from one another. When assembled, the frame portion of the assembly is resiliently supported upon the vehicle wheels by the suspension system and serves as a platform upon which the body portion of the assembly and other components of the vehicle can be mounted. Separate vehicle frame assemblies of this general type are found in most older vehicles, but remain in common use today for many relatively large or specialized use modern vehicles, such as large vans, sport utility vehicles, and trucks. In a typical unitized vehicle frame assembly, the structural components of the body portion and the frame portion are combined into an integral unit which is resiliently supported upon the vehicle wheels by the suspension system. Unitized vehicle frame assemblies of this general type are found in many relatively small modern vehicles, such as automobiles and minivans.
In both separate and unitized types of vehicle frame assemblies, the suspension system resiliently supports the vehicle frame assembly on the rotatable wheels of the vehicle. One type of suspension system that is commonly used in vehicles is a rigid axle suspension system. In a rigid axle suspension system, a single axle beam extends between and is connected to the wheels of the vehicle. To accomplish this, a steering knuckle is pivotably connected to each end of the rigid axle beam. Each of the steering knuckles includes an inwardly extending yoke, which is pivotably connected to the associated end of the rigid axle beam, and an outwardly extending spindle, upon which the wheels of the vehicle can be rotatably mounted. Thus, the steering knuckles permit the wheels of the vehicle to pivot relative to the rigid axle beam to facilitate steering of the vehicle.
The rigid axle beam provides a support surface upon which the vehicle frame assembly can be supported. Usually, one or more resilient spring assemblies is provided between the rigid axle beam and the vehicle frame assembly supported thereon. The resilient spring assemblies allow the rigid axle beam and the wheels to move upwardly and downwardly relative to the vehicle frame assembly. Thus, when a bump or a depression in the road upon which the vehicle is operated is encountered, the resilient spring assemblies accommodate much of the movement of the rigid axle beam and the wheels so as to provide a relatively smooth ride.
Traditionally, the rigid axle beams used in these and other types of vehicle suspension systems have been formed from one or more solid pieces of material that have been formed and secured together into a desired shape. Forging is one known method for forming such rigid axle beams for vehicular suspension systems. Rigid axle beams formed from one or more solid pieces of material are best suited for non-driving applications, i.e., applications where the wheels that are connected to the ends of the rigid axle beam are not rotatably driven by an engine of the vehicle. Thus, solid axle beams of this general type are commonly used as front axle beams in rear wheel drive vehicles and as rear axle beams in front wheel drive vehicles. Although forging and other methods have been used successfully for many years in the manufacture of such non-driving, rigid axle beams, it would be desirable to provide an improved method for manufacturing a non-driving, rigid axle beam for use in a vehicle frame assembly.